Manufacture of zinc dithiocar-bamate amine complexes



Patented July 22, 1952 MANUFACTURE OF ZINC DITHIOCAR- I BAMATEAMINE COMPLEXES JohniC. McGool, Akron, Ohio, assignor to The .B. F. Goodrich Company, New York, N. Y., a

corporation of New York No Drawing, Application November 13, 1950, z Serial No. 195,455

This invention relates to an improved method of preparing known complexchemical compounds heretofore resulting from the reaction of a zinc dithiocarbamate with an amine. Such compounds are also called amine additionsalts of zinc dithiocarbamates and are sometimes referred to herein for brevity simply as complex products or complexes.

It is known that zinc salts of dithiocarbamic acids will react With amines, especially amines which are aliphatic in nature such as alkyl and cycloalkyl amines, to form definitebut'complex chemical compounds of indeterminate structure.

In such complexes, the amine molecule may be joined to the zinc atom by coordinate covalences analogous to the manner in which ammonia is joined tometal atoms in the Well-known metalammonia complexes, but there has beenno conclusive proof of such structure. u f

It is also known that such complex reaction products possess utility as accelerators for the vulcanization of rubber (see S;'Patent-:2, 321,- 301) and as active ingredients in various kinds of 3.5 Claims. (01. 260-429) pesticidal and horticultural compositions (see the I copending application of William DzStewart and John H. Standen, Ser. No. 586,281 filed April 2, 1945 now Patent 2,588,428 and the copending application of Sever L. H0pperstead,, -Ser.fI-l'o. 713,114 filed November 29, 1946" nowQPate'nt 2,600,245. 1 I a The only method heretofore known for preparing such complexes; involves the initial preparation of the zinc dithiocarbamate (in the known manner by reacting a Zinc salt with an-ammonium alkali metal dithiocarbamate) followed by reacting the zinc dithiocarbamate with a molecular excess of the amine, the latter reaction generally being effected by additio'n ofv the amine to a suspension or slurry of the zinc dithiocarbamate in water with vigorous agitatioripand with subsequent refluxingof the mixture after which the reaction mixture is cooled andthe reaction product separatedby filtering...

While this method yields product's suitable for use in accelerating thevulcanizationof rubber, difficulties are encountered when products so prepared, especially on alarge scale, are employed as activeingredients in fungicidal and horticultural compositions. I N One of these dilliculties-.is hatgcompositions containing such products,: when preparedon a by. the complex product. s ot-her; diifiqulty, is

that such products do not form stable aqueous dispersions but rather often result in dispersions in which or more of the complex settles out and is not available for application.

I have now discovered an improved method for preparing the zinc dithiocarbamate-amine complex products. By this new process, the desired product is formed onaycommercial scale; as a finely divided'crystalline "solidflwhich disperses readily and forms a stable dispersion in aqueous solutions of surface active agents'*('wettin and dispersing agents) and is formed asa homogeneous product containing no appreciable unreac ted or free zinc dithiocarbamate:

My improved process for preparing ,the complex products consists of the following steps. First an aqueous reaction medium containing both an amine and a water-solublev dithiocarbamate is prepared. Generally watersoluble salts as the sodium, potassium or ammonium salts of dithiocarbamic acidsswill 'be found most useful because theyyare mo re readily obtainable. It will be found to be; desirable many cases, when the amine is water soluble, to prepare an aqueous solutionof the amine and an aqueous solution of the dithiocarbamate and then combine the two solutions,.for each material willdissolve more rapidly alone; As th'eisecond step, an

. aqueous solution of a water-soluble"- inorganic zinc salt is added'to the aqueoiis'rnedium containing the dithiocarba mate andthe-amineff'ihe resulting aqueous mixture is thenpreferably stirred mildly and heated a b'ove 50 C. for aishort period, preferably l to 2 hours, to'speed up the ner. The total quantities of reactants to; be used in this improved process can bevaried according to the amount of the productdes' ed but the reactants should be employed 'infth'ejprqpq tions of one mole o'fth'e water-soluble inorganic zinc salt for each mole of amineus'ed a mole of amine shouldbe used ior'each two. of water-soluble dithiocarbamate.

The process described above does new involve the formation'of a water-insoluble zinc ,dithiocarbamate as an intermediate but rather the complexproduct is iormeddirejctlyi A s aQresuIt it does not containany'lfr ee orjunre'actedzinc dithiocarbamate as doj complex. products The water-soluble dithiocarbamates which are employed in the process of this invention include any of the sodium or potassium or ammonium I salts of this nature are zinc chloride, zinc sulsalts of dithiocarbamic acids. Dithiocarbamic acids possess the structural formula N-C s SH where each of R and R1 may represent hydrogen or an organic radical, where the R groups are organic radicals each can be the same as in the case of two methyl groups or they each may be diiferent organic groups. Also R and R1 together can be one bivalent organic radical such as pentamethylene or oxytetramethylene. The R groups when individual organic radicals include such representative groups as alkyl radicals, alicyclic radicals, aryl radicals, aralkyl radicals and the like. The water-soluble dialkyl dithiocarbamates, especially the dimethyl dithiocarbamates are particularly productive of useful complex products and are preferred reactants. Other illustrative specific dithiocarbamic acids whose water-soluble salts can be employed as reactants for the process of this invention are for example cyclohexyl dithio carbamic acid, tetra hydrofurfuryl dithiocarbamicacid, benzyl dithiocarbamic acid, diethyl dithiocarbamic acid, dibutyl dithiocarbamic acid, diamyl dithiocarbamic acid, ethyl cyclohexyl dithiocarbamic acid, dibenzyl dithiocarbamic acid, ditetrahydrofurfuryl dithiocarbamic acid, pentamethylene dithiocarbamic acid as -well as the dithiocarbamic acids derived by reactionof carbon disulfide with such amines as di-n-prbpyl amine, diisopropyl amine,

N-methyl cyclohexyl amine, N-butyl cyclohexyl amine,[N-methyl-o-methyl cyclohexyl amine, N-

methyl tetrahydro alpha furfuryl amine, N-butyl tetrahydro alpha furfuryl amine, morpholine,

' symmetrical diethyl ethylene diamine, symmetrical dibutyl trimethylene diamine, N-ethyl-omethyl cyclohexyl amine, methyl propyl amine,

methyl isobutyl amine, 2-ethyl. butyl amine,

but primary and secondary aliphatic and cycloaliphatic aminesare preferred. Specific amines illustrating the scope of amine reactants include methyl amine, ethyl amine, butyl amine, amyl amine, hexadecyl amine, octadecyl amine, di-

'methyl 'amine, diethyl amine, dibutyl amine,

diamyl amine, trimethyl amine, triamyl amine,

4 cyclohexyl amine, furfuryl amine, tetrahydrofurfuryl amine, ditetrahydrofurfuryl amine, N-butyl tetrahydrofurfuryl amine, benzyl amine, mono-otolyl ethylene diamine, di(beta phenethyl) amine, hexahydro ortho or para toluidine, N- methyl cyclohexyl amine, N-methyl tetrahydro alpha furfuryl amine, N-ethyl tetrahydro alpha .furfuryl amine, N-methyl hexahydro o-toluidine,

symmetrical diethyl trimethylene diamine, symmetrical dipropyl ethylene diamine, beta-phenethyl amine, N-methyl isobutyl amine, and the like. The most useful complex products are those obtained using a primary amine especially a primary cycloalkyl amine such as cyclohexyl amine.

Any water-soluble inorganic zinc salt can be employed as the other reactant. Illustrative zinc fate, zinc acetate, zinc bromide and zinc nitrate.

The following specific examples illustrate the preparation of the complex products according to this invention and also illustrate the superiority of the products prepared thereby over the products prepared by the methods suggested and used prior to the discovery of the improved method disclosed in this invention. In all the following examples the term parts is employed to indicate parts by weight.

Example I An aqueous solution containing 26.8 parts (0.2 mole) of sodium dimethyl dithiocarbamate dissolved in 114 parts of water and an aqueous solution containing 10.9 parts (0.11 mole) of cyclohexyl amine in 50 parts of water were added to a reaction vessel. While the aqueous solution was being mildly stirred, an aqueous solution containing 28.7 parts of zinc sulfate heptahydrate dissolved in 30 parts of water was rapidly added to the reactor. The resulting aqueous solution was heated to a temperature between 55 and 60 C. and maintained at that temperature for 30 minutes, after which it was cooled and filtered to recover the precipitated complex product which had formed. This product was washed with water and air dried. In this manner 31.2 parts (a 77.3% yield based on the 0.1 mole zinc sulfate employed of the zinc dimethyl dithiocarbamatecyclohexyl amine product were recovered. This product was found to contain 22.3% chemically combined cyclohexyl amine or, in other words, substantially all the reactants had entered into the complex formation leaving no free zinc dithiocarbamate.

Example II V Example I were again employed, but in this preparation the solution of zinc sulfate was added to' the aqueous solution of sodium dimethyl dithiocarbamate to first form the zinc dithiocarbamate. Then the resulting mixture was heated about.55f C. and stirred vigorously to maintain a uniformslurry of the precipitated zinc dithiocarbamate which formed. Then the aqueous solution of cyclohexyl amine was added. This mixture was maintained at 55 to 60 C. for 30 minutes and was then cooled and filtered to recover the zinc dithiocarbamate amine product which had formed. In this manner only 28.8 parts (a 71.4% yield based on the 0.1 mole zinc sulfate employed) of the desired product was recovered. It was found that this product contained appreciable amounts of free zinc dithiocarbamate.

The following example demonstrates that the product prepared by the method of this invention is superior to that prepared by the method of the prior art.

Ezcample IV An aqueous solution containing about 0.001% by weight of Triton N-l00, a tertiary octyl-phenoxy poly-ether alcohol, as a dispersing agent was prepared. In aliquot portions of this aqueous solution there was dispersed by weight of the products of Examples I, II and III. These three dispersions were allowed to stand for one hour. There were no settlings in the dispersions containing the complex products of Examples I and II but the dispersion containing the complex product of Example III was unsatisfactory for horticultural sprays for it contained considerable solids which had settled out. These solids represented 26.8% of the complex zinc dithiocarbamate-cyclohexyl amine reaction product originally dispersed therein. These settlings were found to contain 18.6% cyclohexyl amine while the solids before being dispersed had contained 21.5% cyclohexyl amine. Thus the product of Example III not only would not form a dispersion suitable for spraying but was not a homogeneous material and thus not a pure chemical compound. Also there was present in the dispersed solids and in the settlings a quantity of free zinc dimethyl dithiocarbamate which is phytotoxic and causes injury and leaf burn, when the dispersion is sprayed on plant life. In contrast, the dispersions of the products of Exthiocarbamate and the amine amples I and II were completely non-phytotoxic.

Although the above specific illustrative examples employed sodium dimethyl dithiocarbamate as a reactant, it will be understood that any water-soluble salt of any dithiocarbamic acid aqueous solution containing substantially two moles of a, water-soluble dithiocarbamate and substantially one mole of an amine selected from the class consisting of alicyclic, aliphatic and saturated heterocyclic amines, adding to this solution an aqueous solution of substantially one mole, of a water-soluble inorganiczinc salt, stirring and heating the resulting solution to a temperature between C. and C. for about one-half to two hours, thereby to produce in a crystalline and substantially pure form a complex chemical compound chemically identical with the product resulting from the reaction of a zinc dithiocarbamate and said amine.

2. The method of claim 1 where the first aqueous solution is prepared by combining an aqueous solution containing substantially two moles of the dithiocarbamate with an aqueous solution containing substantially one mole of the amine.

3. The method of claim 1 where the watersoluble dithiocarbamate is a sodium dialkyl diis cyclohexyl amine.

4. The method which comprises preparing an aqueous solution containing substantially two moles of a sodium dialkyldithiocarbamate and substantially one mole of cyclohexylamine, adding to this solution an aqueous solution containing substantially one mole of zinc sulfate, stirring and heating the resulting solution to a. temperature between 50 C. and 100 C. for about onehalf to two hours, thereby to produce in a crystalline and substantially pure form a complex chemical compound chemically identical with'the product resulting from the reactionof a zinc dialkyldithiocarbamate with cyclohexylamine.

5. The method which comprises preparing an aqueous solution containing substantially two moles of sodium dimethyldithiocarbamate and substantially one mole of cyclohexyl amine, adding to the solution an aqueous solution containing substantially one mole of zinc sulfate, stirring and heating the resulting solution to a temperature between 50 C. and 100 C. for about one-half to two hours, thereby to produce in a crystalline and substantially pure form a complex chemical compound chemically identical with the product resulting from the reaction of zinc di-methyldithiocarbamate with' cyclohexyl amine.

JOHN C. McCOOL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,321,301 Lichty June 8, 1943 2,443,161 Gillette June 8, 1948 

1. THE METHOD WHICH COMPRISES PREPARING AN AQUEOUS SOLUTION CONTAINING SUBSTANTIALLY TWO MOLES OF A WATER-SOLUBLE DITHIOCARBAMATE AND SUBSTANTIALLY ONE MOLE OF AN AMINE SELECTED FROM THE CLASS CONSISTING OF ALICYCLIC, ALIPHATIC AND SATURATED HETEROCYCLIC AMINES, ADDING TO THIS SOLUTION AN AQUEOUS SOLUTION OF SUBSTANTIALLY ONE MOLE OF A WATER-SOLUBLE INORGANIC ZINC SALT, STIRRING AND HEATING THE RESULTING SOLUTION TO A TEMPERATURE BETWEEN 50* C. AND 100* C. FOR ABOUT ONE-HALF TO TWO HOURS, THEREBY TO PRODUCE IN A CRYSTALLINE AND SUBSTANTIALLY PURE FORM A COMPLEX CHEMICAL COMPOUND CHEMICALLY IDENTICAL WITH THE PRODUCT RESULTING FROM THE REACTION OF A ZINC DITHIOCARBAMATE AND SAID AMINE. 